This invention relates to improvements in valves for hemostasis catheter introducers used in the insertion and removal of catheters and guide wires from a patient's blood vessel. More particularly, the invention relates to a self-sealing gasket in a hemostasis cannula that prevents back bleeding with inserted catheter or guidewire devices and further prevents leakage from the cannula after removal of the catheter or guidewire devices.
Angiography is a well-known and very valuable procedure used to diagnosis vascular and organ disease. It involves the introduction of a hollow tubular catheter into one of the major arteries or veins, such as the femoral or brachial arteries, and advancing and maneuvering it into smaller branching vessels which are to be studied. After the catheter is in position, a radio-opaque fluid is injected through the catheter into the vascular system to be studied and an X-ray picture is taken of the now X-ray opaque vascular structure.
Prior art techniques for introducing such catheters include what is known as the "cut down" method and various modifications of the "Seldinger" technique. The "cut down" technique involves surgically opening a vein or artery and introducing the angiographic catheter directly through the incision. This method generally involves the loss of blood through the incision as well as venous ligation and arterial repair. The use of this method renders it particularly difficult to employ the same vessel when multiple studies are indicated.
The American Journal of Cardiology, VOLUME 30, Sep. 1972 at page 378, describes an alternative method of cardiac catheterization, a modification of the Seldinger technique, wherein a percutaneous sheath is introduced into the lumen of a blood vessel. A hollow needle is inserted through the skin and into the lumen; a guide wire is passed through the needle and advanced up the artery or vein into the organ to be studied; the needle is removed, leaving the guide wire in the vessel; a sheath and dilator unit are advanced over the wire into the vessel, and; the dilator is removed along the guide wire. Thereafter, any type of catheter of similar diameter, can be inserted through the sheath into the vessel. To avoid excessive bleeding, and to ensure against the possibility of an air embolism, this technique requires the physician to occlude the orifice of the sheath during catheter changes. The procedure suffers from the possibility of a blood clot migrating to the heart, lungs, or extremities. Blood loss through the annular space between the sheath and the catheter is difficult to avoid.
My earlier invention, described in U.S. Pat. No. 4,000,739, provided a cannula which could be left in the vessel during angiographic or other catheterization procedures while the catheter is manipulated within the cannula and vessel. Generally, that invention featured a hemostasis cannula comprising a body having a passage therethrough adapted to receive a catheter and having a pair of juxtaposed gaskets mounted in the passage in contact with each other. A first one of the gaskets has a round hole, the other a Y-shaped slit. The first or more proximal gasket maintains a sealing relationship with the outer surface of the catheter and, upon withdrawal of the catheter from the passage, the gaskets cooperate to close the passage, since the distal gasket with the Y-shaped slit is compressed against the first gasket. The cannula described there further includes a length of flexible tubing in fluid tight engagement with the body. A port communicating with the body of the cannula for introducing fluids into the patients arteries is also provided.
Other valving arrangements have been demonstrated to be effective for use in catheter introducers such as that shown in U.S. Pat. No. 4,626,245 to Weinstein. There, the hemostasis valve comprises an elastomeric partition made of a single integral piece. A first slit is cut on a first side of the valve while a second slit is cut on the second, opposite side of the piece. The first and second slits are in intersecting relation to each other, each slit having a depth sufficient to permit physical interaction with each other but insufficient to extend through the entire thickness of the partition. The single piece construction of Weinstein sometimes resulted in leakage due to insufficient sealing around the catheter when inserted therethrough. Other leakage sometimes resulted from a build-up of clots between the slits preventing proper closure for a tight seal. This condition is aggravated when the catheter is left in the patient for extended periods.
U.S. Pat. No. 5,304,156 to Sylvanowicz, et al. describes a self-sealing gasket adapted to effect a seal when a catheter or guide wire extends through the gasket as well as when the gasket is empty. Sylvanowicz, et al. modified the gasket arrangement of Weinstein by providing a single piece molded gasket, the outer half thickness of the gasket having a central hole, slightly smaller in diameter than the diameter of the guide wire that will be received in the device for forming a seal about the guide wire. The inner half thickness of the gasket defines a plurality of radially extending slots which extend to a depth slightly greater than to the middle of the thickness of the gasket. The combination of slits and the central hole provide an arrangement which is effective to make a tight seal against a guide wire as well as with much larger diameter catheters without unduly inhibiting movement of either the guide wire or the catheter through the gasket.
Although the above gasketing arrangements are functional as far as preventing unnecessary blood loss while the catheter is inserted through the hemostasis cannula, modern medical practices have placed a new demand on cannula valves requiring additional performance levels which have heretofore been unaddressed. More particularly, the prior medical practice was to allow the hemostasis cannula to remain in place for several minutes or perhaps up to two hours. Currently, however, the cannula may be left in for many hours or over a period of several days at a time. Mainly, the current practice of leaving the hemostasis cannula in place for prolonged periods is for the purposes of facilitating follow-up procedures without the risk of re-entry into the vessel for access.
In practice, the valves used in hemostasis cannula leak to some extent. Even though most leaks are minor and usually not life threatening, they are irritating. Oftentimes, the tricuspid leaflets such as in the valve of my earlier patent identified above do not completely close because they do not perfectly mate. Small blood clots which form on the catheter lodge between the leaflets as the catheter is withdrawn from the cannula. When this happens, the tip of the catheter or vessel dilator must be re-introduced through the gasketing arrangement in order to realign the leaflets forming the tricuspid valve. In most instances, rearranging the leaflets prevents further leakage. However, when the cannula is left in place in a vein or artery of a patient for extended periods, fibrotic tissue can form clots that lodge between the leaflets of the tricuspid valve, causing leakage.